1. Field of the Invention
This invention relates to the mechanical arts. In particular, this invention relates to a cinch-up latch for securing two members, typically an aircraft panel and a keeper, to one another.
2. Discussion of the Related Art
Modern jet engines are usually enclosed by a large cylindrical-shaped structure which typically includes a pair of aircraft cowlings. These cowlings must be able to withstand considerable tension hoop loads caused by the high pressure of the jet exhaust stream flowing through the engine. Typically, the cowlings are hinge-mounted to the upper portion of the engine, near where the engine is mounted to the aircraft via an engine pylon. The cowlings are hinged so that they may be pivoted upward to provide access to the engine for maintenance and repair.
Latches are frequently used to secure aircraft cowlings together by holding the cowlings adjacent to one another or adjacent to an interposed strut at their peripheral edges. These latches must be able to secure the cowlings in place by exerting a large amount of force on compressible seals located between the cowlings or the cowlings and the interposed strut. The size and number of the compressible seals have increased in recent years due to increases in the size of jet engines.
Conventional cowling latches have the disadvantage of requiring either more than one worker, to push the cowlings together closing the gap between the cowlings, or the use of an additional tool called a come-along to close the cowlings. Only after the cowlings are pushed together, can the latch, which has a limited reach, be secured. Another method used to secure the cowlings involves the use of a first latch to help close the gap between the cowlings, and then the use of other latches, having less reach, that further secure the cowlings to each other. The operator must secure the first latch before the other latches are secured. One disadvantage associated with this method is that a typical first latch is considerably larger, heavier, and more costly than ordinary latches. Also, in general, the position of the latch is limited to the ends of the cowlings. Often, as a result of the reach requirements, the first latch has reduced load capabilities after the other latches are secured. Thus, the first latch is carried by the aircraft as extra weight.
Therefore, there is a need for a single latch that can provide an extended range of xe2x80x9cdrawing togetherxe2x80x9d motion for interfacing with a keeper, and be opened and closed by a single latch operator.
In addition, it is desirable to maximize the amount of force that the latch can apply in drawing the cowlings together. Maximizing the amount of force that a single latch can exert also has the added benefit of reducing the number of latches required to secure the cowlings.
However, there are two issues that always need to be addressed in the design of a latch, namely, the dimensional and weight restrictions that are imposed by the aircraft manufacturer. In prior designs, these restrictions severely limited the capabilities of latching devices to apply large forces over the distance required to draw large, modem cowlings together.
In view of the above, it should be appreciated that there is a need for a single latch that can provide an extended range of motion for interfacing with a keeper, that can be opened and closed by a single latch operator, that need not be opened or closed in a particular sequence with other latches, that can provide a large amount of force for drawing aircraft cowlings together, that closely approximate the dimensions and weight of an ordinary latch used to secure aircraft cowlings, and that can be operated in a manner similar to ordinary latches. The present invention satisfies these and other needs and provides further related advantages.
The invention resides in a cinch-up latch that provides advantages over known latches in that the cinch-up latch provides an extended range of motion for interfacing with a keeper, the cinch-up latch can be opened and closed by a single latch operator, the cinch-up latch need not be opened or closed in a particular sequence with other latches, the cinch-up latch provides a large amount of force for drawing aircraft cowlings together, the cinch-up latch closely approximates the dimensions and weight of an ordinary latch used to secure aircraft cowlings, and the cinch-up latch can be operated in a manner similar to ordinary latches.
Preferred embodiments of the cinch-up latch include a bracket, a handle, a trigger lock, a hook, and a linkage. The handle is moveable between a closed and an open position and includes a handle base plate. The trigger lock is pivotably mounted to the handle. The trigger lock engages a keeper when the handle is in the closed position and the trigger lock is disengaged from the keeper when the handle is in an open position. The hook is rotatably mounted to the handle and is used for engaging the keeper. The linkage is rotatably mounted to the bracket, the handle, and the hook. The linkage has an over-center position which prevents the hook from disengaging the keeper. The trigger lock engages the linkage when the handle is in the closed position.
In an alternative embodiment of the present invention, the cinch-up latch includes a trigger spring assembly which interfaces with the handle and the trigger lock. The trigger spring assembly urges the handle toward an open position and the trigger lock toward a position flush with the handle base plate. The hook has a curved end used for engagement with the keeper and an opposing base end which is rotatably mounted to the handle. Also, the hook has a central body located between the curved end and the base end of the hook. Furthermore, a safety curved end is located on the central body of the hook. The linkage of the cinch-up latch is rotatably mounted to the base end of the hook in addition to the bracket and the handle. The safety curved end of the hook engages the linkage when the linkage is in its over-center position.
In another embodiment of the present invention, the bracket includes a pair of mounting ears, having camming surfaces. Also, the handle includes a pair of curved channels, and a pair of rounded ends which contact the pair of mounting ears and ride against the camming surfaces when the handle moves between the closed position and an open position. The linkage also includes a pair of common link interface pins positioned within the pair of curved channels in the handle.
Embodiments of the present invention include a linkage having an elongated link, a pair of connecting links, and a pair of common links. One end of the elongated link is rotatably mounted to the bracket while the opposing end of the elongated link is rotatably connected to one end of the pair of connecting links. The opposing end of the pair of connecting links is rotatably connected to one end of the pair of common links. The opposing end of the pair of common links is rotatably mounted to the handle and the hook.
Another alternative embodiment of the present invention includes a bracket with a curved lip having a pair of bracket notches. The linkage of this embodiment includes a pair of common link curved ends and a pair of common link extensions. The each bracket notch may receive either a common link curved end or a common link extension, thereby, securing the linkage to the bracket.
In another alternative embodiment of the present invention, the bracket has a pair of mounting tabs instead of a pair of mounting ears with camming surfaces. Also, the handle does not include a pair of rounded ends. Thus, in this embodiment, the handle is not designed to make contact with the mounting tabs.
A feature of the invention is that it provides an extended range of motion for interfacing with a keeper, as much as six times the range of motion of ordinary cowling latches. In addition, the dimensions and weight of the cinch-up latch are designed to fall well within the envelope and weight restrictions of an ordinary cowling latch.
Another feature of the linkage of the present invention is that during the initial opening and prior to closing the latch, the linkage maintains the position of the hook such that the hook remains aligned with the direction of the tension load. Also, the linkage allows for the aircraft panel to remain partially open while the hook remains secured to the keeper. This is advantageous since the linkage prevents the handle from being yanked away from the operator""s hand as often occurs when a latch is released over the entire span of the latch.
A further advantage of the present invention is that the hook has a redundant safety curved end which helps to prevent the hook from unlatching when the cinch-up latch is closed. The safety curved end holds the hook securely to the linkage at the point where the linkage is rotatably mounted to the bracket. Also, the linkage of the present invention advantageously allows for hook movement along the direction of the load carried by the hook when the redundant safety curved end engages the linkage.
Other features and advantages of the present invention will be set forth, in part, in the description which follows and the accompanying drawings, wherein the preferred embodiments of the present invention are described and shown, and in part will become apparent to those skilled in the art upon examination of the following detailed description taken in conjunction with the accompanying drawings, or may be learned by practice of the present invention. The advantages of the present invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.